Discovered oddball cylinder bore during rebuild

[pbookey]

Rebuilding a 1972 50 HP Johnson after lower cylinder piston rings failed. Took it to the machine shop today to figure out options of boring, resleeving, etc. Found out that pistons for this engine are hard to find. This is where things got weird. The machinist made a semi-rough measurement of the cylinder bore and came up with 3.075-3.095". SELOC manual states standard for this engine is 3.188". Any ideas on why it would be 0.1" less than standard? And where do i go from here for rebuild, boring 0.1" makes me too nervous!? Thanks in advance.

 

[DHPMARINE]

Re: Discovered oddball cylinder bore during rebuild

get more than a semi-rough reading,no mater who takes it.And check OMC's manual.Seloc may have transposed numbers,or ?<br /><br />DHP

 

[R.Johnson]

Re: Discovered oddball cylinder bore during rebuild

Standard bore, and this is from a 1972 OMC manual is 3.060. If you can get a Wiseco piston at 3.100, which would be .040 over, that would be the way to go if the cylinder will clean up at that diamention. Let's hope that rough measurement was really rough. Don't trust anyone with a wood ruler.

 

[pbookey]

Re: Discovered oddball cylinder bore during rebuild

Thanks for the info. Everything makes sense now. I've pieced together the history of this motor. It has been rebuilt once already and overbored .030, so the measurements, though rough, make sense. The problem now lies in the availability of new pistons, which are very scarce and expensive. Might be to the scrap pile for this one, may not be worth the money to rebuild. I'm starting to look into another motor.